Signaling system



9, 1930. w, TQLSQN 1,784,645 SIGNALING SYSTEM I Filed June- 22, 1928 Inventor. WLlliamATolson, y lid/ His Attorney.

Patented Dec. 9, 1930 UNITED STATES PATENT OFFICE WILLIAM A. roLsoNfor nnxroan, NEW YORK,'.ASSIGNOR '110 GENERALELECTRIC comranygn CORPORATION on NEW YORK SIGNALING SYSTEM Application filed June 22,

My invention relates to signaling systems and more particularly to systems which are adapted for simplex operation, that is, systems which are adapted for alternate trans mission and reception of signals.

Since in systems of the above type, transmission and reception of signals take place alternately a substantial economy, both in initial cost of the apparatus and in the op eration there0f,-may be eifected if, in so far as possible the same apparatus, including the electron discharge devices employed in the system, be utilized during both the transmit aception. A further purpose of my invention is to provide means whereby this may be accomplished with a minimum of annoyance to the operator, resulting from switching operations necessary to efl'ect the desired connections.

The novel features which I believe to be characteristic. of my invention will be set forth with particularity in the appended claims. My invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof may best be understood by reference to the following description taken in connection with the accompanying drawing in which the single figure represents an embodiment of my invention.

Referring to the drawing, 1 and 2 represent electron discharge devices, both of which are illustrated as of the three element type. As will be later described the device 1 operates as a detector during reception and as an oscillation generator during transmis sion. During reception-of calling signals the device 2 operates as a rectifier to currents which are produced'in the output circuit of device 1 and supplies direct current impulses to a calling relay 2. During receptionof .modulator of oscillations 1928. Serial No. 289,552.

voice waves this device is idle and during the transmlssion perlod this device operates as a device 1.

3 represents an oscillatory c1rcu1t COlIlPllS- ing an inductance 4 and condensers 5 and 6.

This oscillatory circuit is connected to conductors 7 which comprise a part of a signal Circuit extending to remote signal apparatus or'to a suitable antenna system as desired. The condenser 5 which comprises a portion of the oscillatory circuit is permanently con-- nected between thegrid and cathode of the discharge device 1. Thus oscillations produced in the circuit 3 in'response to high frequency currents receivedfrom a remote point are impressed upon the grid of the discharge device 1. The oscillatory circuit 3, however, is unassociated, either inductively or. conductively, with the anode of the device 1 at this time and during the entire reception period. In this way the possibility of oscillations being produced in the oscillator during reception by action of device 1, is eliminated. The side of the oscillatory circuit op-.

*posite the grid connection may be connected to the anode by the contacts of I relay 35 during scribed.

A source of potential 8 is connected through choke coil 8 between the cathode and grid of device 1, whereby the grid is maintained at a fixed negative potential with respect to the -.mary winding of coupling transformer 10,"

source of potential 11, conductor'12, cathode conductors 17 and space between the cathode .and anode of the device 1. The secondary winding of the transformer- 10 is connected to the grid of the discharge device 2 through produced by the transmission as will later be de-' cathode. This bias potential is of magnitude a. circuit comprising conductor 13, contacts 14 and 15 of switch 16, secondary winding of the transformer 10, a portion of source of potential 8, cathode conductors 17 and cathode of the device 2. The negative potential impressed upon the grid of device 2 by the source 8 is such that this device also operates as a rectifier of alternating current pro-- 3 from a remote point are impressed upon the grid of the discharge device l-and rectified.

Currents flowing in the output circuit of the device 1 resulting from demodulation of the :20 received high frequency wave are supplied through the transformer 10 to the grid of the device 2. These currents are rectified by the device 2 and supplied to the relay 2'. represents contacts upon the relay 2 which :5 are utilized to control any suitable type of signal device 21 whichmay comprise abell, relay, selector switch, or the like.

As thus arranged the system is in the nor: mal stand-by condition. It will be seen that the receipt from the signal circuit 7 of modulated currents having the frequency to which the-tuned circuit 3 is adapted to respond will produce operation of the bell 21, informing the operator of a received call. The operator upon hearing the bell will remove the receiver 22 from its supporting hook 23. The receiver hook 23 is biased, by means'not shown, to the position opposite to that shown in the drawing and when the receiver is removed therefrom. it assumes the mentioned opposite position and thereby effects the following connections. The anode circuit of the device 2 is connected by means of contacts 18 and 24 to the anode of the (levice 1 through the choke coil 9, the anodes of these devices then being both connected through the primary winding of the transformer 10 and the source of potential 11 to the cathode conductors. The circuit of the relay 2 is broken at contact 18 and operation of the signal device 21 is interrupted. The anode of the device 1 is also connected \through the radio frequency choke coil 9, conductor 25,-c'ont acts 26 and 27 of switch 16, a

blocking condenser 28, contacts 29 on switch 30, receiver 22, conductor 31 to' the cathode conductors 171 Thus in this position of the switch 16 signals are supplied directly from the anode circuit of the device 1"to the re- 6 ceiver 22 and the system is in condition for.

reception of voice waves or other signal current by which the received carrier wave is modulated.

Since the device 2 isidle during this cond1- tion of the receiving circuit, connections with its potentiometer 32', which may be utilized for volume control purposes, its connected in a circuit leading from the cathode conductors 17 through contacts 33 and 14 on the switch 16 to the grid of the device 2.

When the operator desires to talk he will press and retain the button 30 in its lower position and speak into the microphone 34-. By means of contacts 29 the circuit of the receiver 22 is interrupted. Relay 35 is encrgized through a circuit extending from the positlve side of the source of potentlal 36 through relay 35, contacts 37 and 38 on switch 30 to the negative side of the source of potential 36. Relayv35 then actuates its armature to the right, thereby connecting the oscillatory circuit 3 between the grid and anode of the discharge device '1 through blocking condenser 39. The circuit of the transmitter 01'. microphone 34 now extends from the positive. side of the source of potential 36 through the primary winding of the microphone transformer32, transmitter 34, contacts 40 and 41. of switch 42, contacts 43, 37 and .38 of the switch 30, all-of which are in conductive engagement with each other and conductor 31 to the negative side of the source .of potential 36.

Thus with the receiver 22 removed from the hook and the switch 30 pressed to its lower position, voice currents may be supplied from the transmitter through the microphone transformer 32 to the grid of the electron discharge device 2. The coupling transformer.

10, the primaryof which is connected in the anode circuit of both discharge devices operates as a modulation reactor to modulate the high frequency currents in accordance with the voice waves produced by the. transmitter.

It will thus be seen that duringthe conversation the only switchingmeans which the operator need bear in mind,or control, is the switch 30. To transmit he need merely to press the switch 30 and to receivehe releases the switch 30. All of the changes in the con- Q nections of device 2 necessary to cause this device to assume the modulating function, or the rectifying function as desired are made in response to the position of the receiver hook. The only additional connections which are necessary are in the receiver circuit, the microphone circuit and the circuit of relay 35 for controlling the. tube 1. These latter connections may be made by means of light contacts which 'may be operated by a small button mounted upon the telephone instrument and which may be controlled by the finger of the operator during the conversation.

Theswitch 42, which is also a small button mounted on the telephone instrument is used to complete the circuit of the ringing current generator 44, 46 through the keying contacts 48. The ringing current generator comprises an ordinary induction coil of well known construction which produces alternating currents in the circuit of blocking condenser 46, contacts 48 and the primary of the microphone transformer.

To send signals for thepurpose of calling a remote party the operator will remove the receiver 22 from the hook, operate both switches and '42 to their lower position and then dial the number of the called party by means of the dialing or keying device 43.

With the key 42 in the lower position, the circuit of the microphone is vopened at the contacts and 41 and a circuit is closed from the positive side of the source of potential 36 through the inductance coil 44 and its armature and contact, contacts and 41 of the switch 42, contacts 43, 37 and 38 of the switch 30 and conductor 31 to the negative side-of the source of potential 36. The coil 44 will (ill then be energized and will attract its armature thereby interrupting its'own energizing circuit, which, in turn, causes its contacts to close, this buzzer action continuing as long as the key 42 is in its lower position. Due to the inductance of the coil 44 oscillatory currents will be produced in a circuit extending from the positive side of the source of poten-- tial 36 through coil 44, condenser 46, contacts 47 of key 42, contacts 48 of the dialing device 43, primary winding of the microphone transformer 32 to the positive side of the source of potential 36. These oscillatory currents will be supplied to the grid of the discharge device 2 and, in a well known manner, will'be caused to modulate the high frequency currents of the circuit 3 whenever the contacts 48 are in engagement. These contacts may be actuated in accordance with any desired code. combination by the device 43. Having efi'ected the necessary dialing the operator'will release the buttons 42 and 30 and listen for a response from the remote operator.

It will be seen that with the circuit as thus described the operator may efl'ect the necessary connections with great facility, most of the connections being made in response to the position of the receiver hook. The receiver having been removed from the hook the only additional operation on the part of the operator, to change the circuit from its receiving condition to its transmitting condition is to press the key 30. It is preferable that the receiver 22, the transmitter or microphone, 34 and the switching devices 30 and 42 be mounted in a single unit supported by the receiver hook 23.- The operator may then by means of the fingers on the hand in which he holds the receiver efiect with convenience all of the .desired connections.

While I have shown a single embodiment of my invention it will be understood that I do not wish to be limited thereto since many modifications,'both in the circuitarrangement and in the instrumentalities employed -may be made without departing from the spirit and scope of my invention as set forth v current received from a remote point to said second discharge device to causedesired actuation of said signal devices, an oscillatory circuit associated with said second dischargeclevice whereby oscillations may be produced and means including said first discharge device for modulating the oscillations produced.

2. In combination, a plurality of electron discharge devices, each of said devices having an anode, a cathode and a grid, means including an inductance device connected in the anode circuit of one of said devices and in the grid circuit of a second device whereby said devices are connected in cascade relation, a signal device connected in the anode circuit of said second device, means for supplying current received from a remote point to the grid of said first device to cause actuation of said signal device, an oscillatory circuit, means for connecting said oscillatory circuit to the grid and anode of said first device whereby oscillations may be produced and means including said second discharge device and said inductance device for modulating said oscillations.

3. In combination, a plurality of cascade connected electron discharge devices, an oscillatory circuit connected to the grid and cathode of one of said discharge devices, saidv oscillatory circuit being normally unassociated with the anode of said device, said last mentioned discharge device being arranged to rectify high frequency currents supplied to said oscillatory circuit from a remote point, a signal device, means including a second of said discharge devices for rectifying current produced in the anode circuit of said first device and for operating'said signal device in response thereto, means for conduetively connecting said oscillatory circuit between the grid and anode of thefirst device whereby high frequency current may be produced and means including said second discharge device for modulating said oscillations in response -to s gnal current.

. 4. The combination in a high frequency signaling system, an electron discharge device having an anode, a cathode, and a grid, an oscillatory circuit connected to the cath- 5 ode and grid of said discharge device, said discharge device being arranged to rectify said grid and anode whereby oscillations may be produced by saiddischarge device and means forniodulating said oscillations in re.- sponse to signal current.

5. In a signal system, an oscillatory circuit, a signal device, a plurality of normally cascade connected electron discharge devices,

each of said discharge devices having an anode, a cathode and-a grid, said oscillatory circuit being normally connected to the grid and cathode of one of said devices and unassociated with the anode of said device, means including said cascade connected discharge devicesfor rectifying current supplied from a remote point to said oscillatory circuit and 80 for operating said signal device in response thereto, a second signal device, a transmitter,

: a common switching means for connecting the output of said one of said devices to said second signal device and for connecting the anodes .of said devices together and additional switching means for connecting said transmitter to the grid of another of said devices and for connecting said oscillatory circuit between the grid and anode of said firstdischarge device whereby high frequency currents modulated in response to currents produced by the transmitter may be produced in said oscillatory circuit for transmission to a remote point. 6. The combination in a high frequency telephone system, a; pair of electron discharge devices, an oscillatory circuit connected to the grid and cathode of one of said discharge devices whereby oscillations in said circuit are impressed upon said grid, a signal device, means including the other of said discharge devices for rectifying currents produced in the anode circuit of said first device and for supplying direct current to said signal device in response thereto, a transmitter, a second signal device, a transformer, means responsive to the position of the receiver hook for connecting said. second signal device in the output circuit of said first discharge device, for connecting the anodes of said devices together and for connecting the secondary of said transformer to the grid of said other discharge device and additional switching means for connecting said oscillatory circuit be- I 5 tween the grid andanode of said first device and for connecting said transmitter to the primary of said transformer whereby high frequency current modulated in accordance with currents produced by said transmitter are produced in said oscillatory circuit.

7. In combination, a pair of electron discharge devices, an oscillatory circuit connected to the grid and cathode of one of said devices, means for impressing a fixed bias potential upon the grid of said device, a sigfor connecting said second signal device in the anode circuit of said one discharge device and for connecting the primary of said transformer in the anode circuit of both of said devices, a transmitter, means for. conductively connecting said .oscillatory circuit between the grid and anode of said one discharge device and for connecting said transmitter in the grid circuitof the other discharge device whereby high frequency current produced in said oscillatory circuit is modulated in accordancewit-h current produced by said transmitter.

8. In combination, a pair of electron discharge devices, each of said devices having an anode, a cathode and a grid,'a signal circuit including an oscillatory circuit connected to the grid and cathode of one of said discharge devices, a signaldevice connected in the anode'circuit of the other discharge device, an inductive coupling between the anode of said first device and the grid of the other device whereby said signal device is oper ated in response to current supplied from a remote point to said oscillatory circuit, a second signal device, and switching means whereby said coupling means is connected in the anode circuit of said second discharge device, said second signal device is conneeted in the grid circuit of the second discharge device and said oscillatory circuit is connected between the grid and anode of said first device whereby high frequency currents produced in said oscillatory circuit by said first device are modulated in response to operation of said second signal device and supplied to said signal circuit.

In witness whereof, I have hereunto set my hand this 21st day of June, 1928.

WILLIAM A. TOLSON. 

